On Tue, Sep 2, 2008 at 1:18 PM, Chris Tyler <chris@xxxxxxxxxxx> wrote: > > On Tue, 2008-09-02 at 13:26 -0600, Phil Meyer wrote: >> All that, to say this: a single slow USB device on a controller will >> cause the controller to drop to slow (USB 1.1) mode. Not just a single >> port drops, the whole controller drops. > > Slightly expanded: > > (a) USB 1.1 vs. USB 2.0 isn't directly related to speed -- USB 1.1 > supports low (1.5 Mbps) and full (12 Mbps) speeds; USB 2.0 adds support > for high (480 Mbps) speed. USB 2.0 devices don't *have* to operate at > full speed, though -- e.g., a true USB 2.0-certified keyboard is still > going to send your scancodes to the host at low speed. > > (b) Using a low- or full-speed device doesn't force that controller > (actually pair of controllers - EHCI+UHCI) into a low- or full-speed > mode -- low-/full- and high-speed connections can be interleaved. > However, USB is a shared bus, and use of the bus is scheduled in time > slices, so as an example transferring 8 Mbps at full speed (plus control > overhead) will use the bus just over 2/3rd of the time, reducing the > time available for full speed transfers to less than 1/3 (<160 Mbps), > yielding a total throughput of under 168 Mbps. This can be alleviated by > using a hub with a transaction translator, which will buffer low- or > full-speed transfers and send them in bursts to the host at high speed > (and vice versa for data coming from the host) to mitigate the impact of > the low- and full-speed devices on the high-speed ones. > > >> This problem used to be very problematic when most USB mice and >> keyboards were USB 1.1 >> >> Now days, all USB devices should say 2.0 on them somewhere. > > Even a Certified USB 2.0 mouse will operate at low speed (I haven't seen > any 480 Mbps mice!). For example, from /proc/bus/usb/devices on my > desktop: > > T: Bus=01 Lev=02 Prnt=03 Port=02 Cnt=03 Dev#= 9 Spd=1.5 MxCh= 0 > D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1 > P: Vendor=046d ProdID=c00e Rev=11.10 > S: Manufacturer=Logitech > S: Product=USB-PS/2 Optical Mouse > C:* #Ifs= 1 Cfg#= 1 Atr=a0 MxPwr= 98mA > I:* If#= 0 Alt= 0 #EPs= 1 Cls=03(HID ) Sub=01 Prot=02 Driver=usbhid > E: Ad=81(I) Atr=03(Int.) MxPS= 4 Ivl=10ms > > Note the "Ver= 2.00" in the D: line (USB version 2.0), but "Spd=1.5" in > the T: line (low speed, 1.5 Mbps). > > -Chris Checking on the speed was interesting. The /proc/bus/usb/devices shows that both devices rut at 480Mbps. It appear the the usb stick is having a problem from too many read/writes. It's been a while since I've been using. FROM DVDRW T: Bus=01 Lev=01 Prnt=01 Port=03 Cnt=01 Dev#= 10 Spd=480 MxCh= 0 D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 P: Vendor=054c ProdID=02d1 Rev= 0.00 S: Manufacturer=Sony S: Product=DRX-830U FROM MEMORY STICK T: Bus=01 Lev=01 Prnt=01 Port=05 Cnt=02 Dev#= 11 Spd=480 MxCh= 0 D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1 P: Vendor=0457 ProdID=0151 Rev= 1.00 S: Product=USB Mass Storage Device thanks for the enlightenment ~af -- fedora-list mailing list fedora-list@xxxxxxxxxx To unsubscribe: https://www.redhat.com/mailman/listinfo/fedora-list Guidelines: http://fedoraproject.org/wiki/Communicate/MailingListGuidelines
